Acyl-lipid desaturases and Vipp1 cooperate in cyanobacteria to produce novel omega-3 PUFA-containing glycolipids

Leslie B Poole,Floyd H Chilton,Derek Parsonage,Susan Sergeant,Jingyun Lee,Cristina M Furdui,Leslie R Miller

doi:10.1186/s13068-020-01719-7

Leslie B Poole, Floyd H Chilton + Show 5 more

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https://doi.org/10.1186/s13068-020-01719-7

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Abstract

BackgroundDietary omega-3 (n-3), long chain (LC-, ≥ 20 carbons), polyunsaturated fatty acids (PUFAs) derived largely from marine animal sources protect against inflammatory processes and enhance brain development and function. With the depletion of natural stocks of marine animal sources and an increasing demand for n-3 LC-PUFAs, alternative, sustainable supplies are urgently needed. As a result, n-3 18-carbon and LC-PUFAs are being generated from plant or algal sources, either by engineering new biosynthetic pathways or by augmenting existing systems.ResultsWe utilized an engineered plasmid encoding two cyanobacterial acyl-lipid desaturases (DesB and DesD, encoding Δ15 and Δ6 desaturases, respectively) and “vesicle-inducing protein in plastids” (Vipp1) to induce production of stearidonic acid (SDA, 18:4 n-3) at high levels in three strains of cyanobacteria (10, 17 and 27% of total lipids in Anabaena sp. PCC7120, Synechococcus sp. PCC7002, and Leptolyngbya sp. strain BL0902, respectively). Lipidomic analysis revealed that in addition to SDA, the rare anti-inflammatory n-3 LC-PUFA eicosatetraenoic acid (ETA, 20:4 n-3) was synthesized in these engineered strains, and ~ 99% of SDA and ETA was complexed to bioavailable monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) species. Importantly, novel molecular species containing alpha-linolenic acid (ALA), SDA and/or ETA in both acyl positions of MGDG and DGDG were observed in the engineered Leptolyngbya and Synechococcus strains, suggesting that these could provide a rich source of anti-inflammatory molecules.ConclusionsOverall, this technology utilizes solar energy, consumes carbon dioxide, and produces large amounts of nutritionally important n-3 PUFAs and LC-PUFAs. Importantly, it can generate previously undescribed, highly bioavailable, anti-inflammatory galactosyl lipids. This technology could therefore be transformative in protecting ocean fisheries and augmenting the nutritional quality of human and animal food products.

Highlights

Dietary omega-3 (n-3), long chain (LC, ≥ 20 carbons), polyunsaturated fatty acids (PUFAs) derived largely from marine animal sources protect against inflammatory processes and enhance brain development and function
We hypothesized that Δ15 Acyl-lipid desaturase (DesB) and Δ6 Acyl-lipid desaturase (DesD) overexpressed from a plasmid would impart or augment stearidonic acid (SDA) synthesis in most cyanobacteria
Previous studies reveal that these desaturase reactions occur within thylakoid membranes, and a thylakoid membrane formation enhancer gene, vipp1 [38, 43], was the third protein selected for overexpression to potentially boost levels of newly synthesized PUFAs formed by the enhanced desaturase system

Summary

Introduction

Dietary omega-3 (n-3), long chain (LC-, ≥ 20 carbons), polyunsaturated fatty acids (PUFAs) derived largely from marine animal sources protect against inflammatory processes and enhance brain development and function. With the depletion of natural stocks of marine animal sources and an increasing demand for n-3 LC-PUFAs, alternative, sustainable supplies are urgently needed. Fish represent the predominant source of n-3 LC-PUFAs; wild caught fish are at or beyond exploitable limits, and more than half of fish consumed are farmed [7]. Krill oil as another unsustainable source of n-3 LC-PUFAs exerts even greater strains on the global health of ocean fisheries. There is a growing need for dietary n-3 PUFAs and n-3 LC-PUFAs in terrestrial livestock to enrich levels in meat, milk and egg products [12, 13]

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